Telephone-exchange system



S. B WILLIAMS, JR

TELEPHONE EXCHANGE SYSTEM m. 16, 1923. mums Original Filed April 17, 1918 8 Sheets-Sheet 1 //7 van/0r. 54/7706/ 8. WWW/775 J/ & Y amme @cfi. 16, 1923.

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TELEPHONE EXCHANGE SYSTEM Original Filed April 17, 1918 8 Sheets-Sheet 3 [1 MM 3g EIIIIHP Hume Z.

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TELEPHONE EXCHANGE SYS TEM Original Filed April 17, 1918 8 Sheets-Sheet 5 lflfifils S. B. WILLIAMS, JR

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TELEPHQNE EXCHANGE SYSTEM Original Filed April 17, I918 imnms 8 Sheets-Sheet ck. 16, 1923. 2,471,018 S. B. WILLIAMS, JR

TELEPHONE EXCHANGE SYSTEM Samoa/5 [MW/4075 z/r.

ERMMAfIj? tobea Patented Oct. E6, 1923.

TATES SAMUEL IB. WILLIAMS, J R, OF BROOKLYN, NEW YORK, ASSIGNOR TO WESTERN ELEC- TRIO COMPANY, INCORPORATED/OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

Original application filed April .17, 1918, Serial NO-' 229,035, Patent No.

1921. Divided and this application filed May 14, 1921.

To all whom it may concern:

Be it known that I, SAMUEL B. WILLIAMS, Jr. a citizen of the United States, residing at l3rooklyn, in thecounty of Kings, State of New York, have invented certain new.

and useful Improvements in Telephone- Exchang Systems, ofwhich the following is a full, clear, conclse, and exact description.

This invention relates to improvements in telephone exchange systems and has particular reference to systems of the type employing automatic switches for distributing calls from telephone lines tothe connecting circuits of operators positions. I

The claimed is a division of Patent No. 1,400,120, issued December 13, 1921.

An object of the invention is to provide a system wherein an indication shall be automatically given an operator with respect to the class of service of the calling line and wherein the operator is provided with means for ascertaining the identity of the calling, line, the class of service indication and line identifying means being controlled over a common conductor in such a way that neither will interfere with the other.

Another object is the provision of aclass of service device, which, during its resetting operation, will be unresponsive to other calls and render the operators positionunselectable.

of the following description when taken in connection with the acco-mpanyingdrawings which illustrate what is now believed preferred embodiment of the invention.

In the drawings, Figs. 1 to 7, inclusive, taken together, and arranged side. by side in the manner indicated by the linesthat extend to the margins of the drawings, illustrate as much of the complete organization of'the system as is necessary to enable the construction and mode of operation to be understood. F igs. 8'to 12, inclusive,show different views of the class0frservice switch, Fig. 8 being a bottom plan. view, Fig. 9

l a side elevation, Fig. 10 a top plan view,

Fig. 11 a detail of the armature and driving mechanism and Fig. 12 a detail of a portion of the contact bank with its associated Wipers.

invention herein described and Other objects will appear in the, course TELEPHONE-EXCHAN GE SYSTEM.

1,400,120, dated December 13, Serial No. 469,492.

Two telephone lines are indicated in each of the two groups LG and LG shown in Fig. 1, it being understood that each group may comprise a number of such lines. The ordinary practice is to give the finder-switch brushes access to the terminals of 500 lines, these lines beingdivided into'ten groups of lines each. Each of the groups of lines has associated with it a distributor-switch 130 to the stationary contact terminals of which the lines of that group extend, the brushes of the distributor switch being connected with group apparatus which is actuated by the passage of the brushes over the terminals of a calling line. For a more complete understanding of the switch 130, reference is made to the above-mentioned patent. Each of the lines has associated with it at the central ofiice, a connection register 92 or a resistance coil 91. line is also provided with one or more spring-jacks 14 by means of which connection maybe made with the line when it is called. The lines represented as calling lines in Fig. land the line indicated as a called line inFig. 7, may be lines of. the

the lines also has connection with and is represented by a lamp on a common lamp board 15.

The groups of lines have access to groups of connecting circuits through the medium of'finder circuits F, F and F These finder circuits terminate upon the brushes of pairs of finder and selector switches,

of which two sets, LF and CS and LF and US, are shown. The starting of the finder switches to find the calling lines is effected by the distributor-switch apparatus through the medium of starting apparatus, including the relays 20, 23 and 24, which is common to all of the line groupsand to all of the finder circuits having access tothe lines of these groups. Each of the groups of connecting circuits, to which the groups have access by way of the finder circuits F, F and F is associated with a particular operators position. The appalines of the various being similarly organized and connected.

The multiple connection of the connecting circuit with the terminals of the cord selector switches are shown in the 'case of the connectin circuit that is completely illustrated and in the case of a single connecting circuit that is indicated in another group; and in like manner the multiple connections of the telephone line with the terminals of the line-finder switches are shown in the case of the lines that extend from stations A and A. The multiple connections that exist between corresponding sets of switch I terminals in the case of the other connecting Fig. 3.

. selector switches circuits and telephone lines are omitted in order to simplify the drawing.

A number of groups of cord-selector switches, like the group illustrated in Fig. 3, may have access to the same groups of connectin circuits and their corresponding operators positions. This is indicated in Each of the groups of cord-selector switches has associated with it certain selection-controlling apparatus, that associated with the cord selectors shown in Fig. 3, appearing under the caption frame 2, and that associated with another group of cordappearing under the caption frame 1. The selection-controlling apparatus for each frame or group of cordselector switches comprises a pair of relays 77 and 93 for each group of connecting circuits or operators position, to which the cord selector'has access, and a group of relays 61, 63, 64, 66 and 67 common to all of the first-mentioned groups.

Each of the operators positions is provided with apparatus which is common to all of the connecting circuits of that position, and which may be brought into association with any of the connecting circuits either automatically in the extension of a call to one of the connecting circuits, or at the will of the operator in the course of her supervisory operations. The operators common or position apparatus'is illustrated on Fig. 5 and Fig. 6, and each of the connecting circuits with which the operators position is equipped may have connection with the position apparatus in the same way in which the connecting circuit illustrated in Fig. 4 is shown to have connection with this apparatus.

The line finder and cord selector switches are alike in all substantial respects. Each comprises a longitudinally movable shaft 1, carrying as many sets of brushes 2 as there are groups of stationary terminals to be engaged. To move the shaft up, an extension at the lower end of the shaft is brought into engagement with the constantly rotating power member 3 by means of an idler wheel operated by the up-drive magnet 32; and to move the shaft down, the extension is brought into engagement with the power member 4 bymeans of an idler wheel operated by the down-drive magnet 62. Normally, the brushes of each of the sets 2 are held apart so as to clear the associated terminals by means of a separating cam 5 located between the innermost brushes of the set'. The cam 5 is rotatably mounted, and when rotated in one direction, releases the brushes and permits them to engage the associated terminals. The tripping or releasing of the brushes is controlled by a number of trip magnets, as 16 and 17 Each of these when energized, rotates an associated tri switch shafts 1 and carries as many trip yokes 7 as there are finder switches or selector switches in the group. The trip rod in rotating brings all of its trip yokes 7 into position to operate the brush-controlling cams 5 of the corresponding sets of brushes on all of the switches, so that whichever of the finder switches is caused tomove up, has that set of brushes tripped that corresponds with the particular trip magnet 16, 17, that is at the time energized. \Vhen the finder switch that has been in use is returned to its normal position, any of the associated controlling cams 5 that has been tripped, is engaged and rotated in a reverse direction to separate its switch springs again and thus render them inactive. Each of the line finder and cord selector switches has associated with it, a commutator 8 which comprises a number of stationary commutator segments and a set of movable brushes carried at the top of the switch shaft 1 and cooperating with the stationary segments. This commutator serves to make and break a number of the controlling circuits in the various stages of the upward movement of the switch shaft.

' For controlling the circuits of the organization, there are employed a number of sequence switches which are shown at differ ent points and designated 200, 300, 400 and 500 respectively. These sequence switches may be of the type disclosed in Patent 1,127,808, issued February 9, 1915 to Reynrod 6 that extends transversely to the olds and Baldwin. Each consists of an electromagnetically controlled motor or driving mechanism and a number of associated switch ca'ms. The switch cams, associated with each of the sequence switches 200 are designated 201 to 221 inclusive; those associated with each of the sequence switches by'the cams 171 to 300 are designated 301 to 321 inclusive; those associated with each of the sequence switches 400 are designated 401 to 421 inclusive; and those associated with each of the sequence switches 500 are designated 501 to 507 inclusive. To each of the contacts associated with the various sequence switch cams are applied certai numerals. These numerals in the case of the cams 201, 301, 401 and 501 indicate the only positions of the associated sequence switch in which these particular contacts are open; the numerals applied to all of the other contacts of each se uence switch indicate the only p0Sl-' tions 0? the particular sequence switch in which the associated contacts are closed.

The resting positions of the difierent sequence switches, and the stages of operation with which these positions are associated, are as' follows Finder sequence switch '200.

1 Normal, q

2 Awaitin'g'starting circuit. 3-Hunting. V

4 Awaiting selector sequence switch. 5Talking.

' 18 Finder switch return.

' Selector-sequence switch 300.

1 Normal. 7 i T 2 Awaiting preceding circuit. p

3 Awaiting setting of operators selecting circuit. 9 v V .4 Pass by.

5 Awaiting release of operatofls selecting circuit. 7 1

6 Hunting connecting circuit.

7 Awaiting listening key sequence switch.

8 Awaiting finder sequence switch.

9 Talking.

18 Selector switch return.

Listening hey sequence switch 400. l

Calif/mg cord sequence switch 500.

1 Normal. 2 Awaiting connection. 16'Talking. 1 v V q The class-of-service interrupter comprises number of sets of switch springs o erated 177, inclusive. h lach'of the sets of switch springs associated with cams 172 to 176, inclusive, consists of two The wipers 272, 27 2 springs the contacts of which are normally in engagement. Each of the two sets associated with the cams 171 and 177 consists of two springs the contacts of which are normally 0 en. The cams 172 to 176, inclusive, are so ormed as to cause one, two, three, four and five breaks per revolution respectively in the normally closed circuits controlled by the associated sets of switch springs. The cams 171 and 177 are so formed as to cause one closure per revolution and six closures per revolution, respectively, in the circuits controlled by the associated switch springs; The cam 171 and its associated switch springs control the production of the pick-up impulses, the cam 177 and its associated switch springs control the production of the reset impulses, and the cams 172 to 176 and their associated switch springs control the production of the class-of-service impulses, as will be described hereinafter.

The class-of-service switch, shown in Figs.

8 to 12, inclusive, is of the so-called Dietl type. It includes'three' sets of brushes or wipers, 272, 272 and 272 carried on a common insulating hub mounted on the spindle 269, and radiating at an angle of one hundred and twenty degrees from each other. These brushes or wipers engage a circular row of contacts 274 and insulated segments 273, 273 and 273 Each of the segments 273 extends over a little less than one-third of the circle, there being in the specific switch illustrated, sixteen contact terminals opposite each segment and two contact terminals opposite the space which lies between each. segment and its adjoining segment. and 272 are insulated from each other, and each wiper consists of two switch springs or brushes that are electrically connected so that each wiper serves to connect the. particular contact terminal which it engages with the contact segment which lies opposite that terminal. The radiating wipers are unidirectional in their movement,-so that each wiper co operates succemively with the three segments and their associated contact terminals.

The rotation of the spindle to cause themovement'of the wipers is efi'ected by means of the electromagnet 271 acting through V the medium of the ratchet wheel 279 and pawl 275. The'pawl 275 is carried upon an arm secured to the armature 278 of the electro-- magnet 271. The armature 278 is centrally pivotedso as to be oscillated when the electromagnet is energized, and is returned to its normal position upon the deenergization of the magnet by the helical spring 276, the tension of which may be adjusted by the wing 268. The contact terminals with their associated' contest egments and brushes or wipers are'm'ounted upon l t @7 3 can,

ried upon the supporting frame 270'. The electromagnet 271 with its associated armature, \ratchet wheel and spindle are mounted upon a plate 270 which plate is secured to the plate 270 by a screw and slot connection. The driving or operating parts of the switch and the circuit-controlling parts of the switch are therefore readily separable from each other and from the supporting frame. The operating circuit of the electromagnet 271 is carried to the electromagnet through the knife switch 271, so that the circuit is automatically broken and made as the plate-carrying magnet is removed from and replaced upon the plate 270.

In outline, the operation of the'system in the embodiment disclosed is as follows iVhen a subscriber calls, the passage of the brushes of the distributor switch 130 over the terminals of the calling line records the call in the distributor apparatus of the associated group, and this recorded call causes the closing of the starting circuit common to all of the distributor groups and to all of the line-finder switches that serve these groups, and also causes the energization of the finder switch trip magnet corresponding to the groups of lines in which the calling line is located. If the starting circuit is at the time being used by some other calling line, the recorded call is held until the starting circuit is freed. As soon as the call is discharged into the starting circuit, the distributor apparatus is released and made .available for recording another call in the same group.

The finder switches each have as many sets of brushes as there are groups of lines. The closing of the starting circuit causes a-preselected one of the finder switches to move its-brushes, and the energization of the trip magnet makes active the set of brushes corresponding with the group in which the calling line is located. The apparatus which brings about the energization of the trip magnet operates to prevent temporarily the trip magnetsof other groups of lines from being energized by calls that may at the time be initiated in the other groups.

As soon as the brushes of the finder switch are tripped another finder switch is brought into operative relation ith the starting circuit, and the starting circuit is released and made available forthe use of calling lines in groups other than the group in which the first-mentioned calling. line is located. When the new finder switch is connected with the starting circuit, any vother finder switch is preventedfrom being brought into operative relation with the starting circuit, so that the starting circuithas control over only one finder switch at a time.

When the brushes of the started finder switch complete connection with the terminals of the calling line, the finder circuit operates certain apparatus that determines to which of a number of operators positions the connection of the calling line is to be extended. The selection of the operators position is effected through the medium of selection-controlling apparatus that is common to the cord selector switches upon which the finder circuits terminate, and to the operators positions to which these cord selector switches are designed to extend calls. The selection-controlling apparatus is continuously under the control of the operators positions, and keeps a path prepared for energizingthe trip magnet representing the first available position in the series. The

finder circuit that is extending the call sends a tripping impulse over the path thus prepared, and when the trippin magnet operates, the upward movement 0? the cord selector switch is started. At the outset of this movement the set of brushes is tripped that corresponds with the preselected operators position, and immediately thereafter the common selection-controlling apparatus is released and made available for controlling the selection of other operators positions by other cord selector switches and finder circuits. Durin this selecting operation, the setting of t e selection-controlling apparatus is maintained, so that the tripping impulse is prevented from passing to the trip magnet of some other position which in the interval may have become available. If all of the operators positions should be unavailable at the moment the finder circuit is ready to extend the connection, the finder circuit is held and the availability of the op erators positions is periodically tested by the selection-controlling apparatus until one of the positions becomes accessible, when the operation is proceeded with.

After the set of cord selector brushes has been tripped, it continues its upward movement, successively engaging the terminals of the connecting circuits located at the operators position that has been selected, and steps upon the terminals of the first connecting circuit encountered that is idle and available for use; If for any reason, the brushes should fail to be stopped upon the terminals of a connecting circuit, the cord selector switch is returned to its normal position, and the selecting operation is then repeated.

Prior to the extension of the connection to the connecting circuit, and at the instant that the operators position is selected and the corresponding trip magnet energized, a signal is displayed at the operators position which notifies the operator that her position has been selected and that a call is coming. At the same instant, a by-path is closed that puts the operator immediately into telephonic communication with the calling subscriber, and the listening-in keys associated with all of the connecting cords of the listening keys to receive.

line that is called for and,

ing lme 1s a measured service line,

the position are'rendered inoperative so that the operator cannot interfere with the coming call by listening in on a cord'circuit after the position has been selected and before the call arrives. The operators position at the same time is made inaccessible to other incoming calls.

When the cord selector switch stops on the terminals of the selected-connecting circuit, it lights a lamp associated with that circuit at the operators position, and substitutes a direct path to the operators telephone for the by-path that was closed when the position was selected. At the same time, impulses pass from the subscribers line to class-of-service signal mechanism at the operators position, which mechanism is thus operated to inform the operator. of the class of's'ervice which the calling line is adapted nal is displayed, the calling first notified the operator that her position had been selected, is withdrawn, and means forenabling the operator to inform herself of the identity of'the calling line is made operative. The operators control over has in the meanwhile been restored so that she may, if she desires, listen in on any other connection.

When the operator has received the calling subso'ribers instructions she tests the if it is free, in-

serts the calling plug into the called line spring-jack. This act automatically. brings about the disconnection of the operators telephone apparatus from the circuit and the restoration of the class-of-ser-vice signal mechanism, the operators position being rendered unselectable and the class-of-service mechanism being prevented from being brought into operative relation with any connecting circuit while the restoration-is being effected. a

When the subscribers have finished their conversation, the operator efi'ects disconnection by pressing the disconnect keyand withdrawing the calling plug. If the callthe operator presses a key which registers the call on the line register and the position register upon the depression of the key and releases the connection upon. the release of the key. This key is effective to apply register operating current to the connecting circuit only when the connecting circuit is extended to a calling line. i If the calling subscriber wishes a second connection, the operator presses another key which registers the call on the line and position registers, but does not disconnect the calling line from the connecting circuit. Before performing the disconnecting or registering operations referred to above, the operator supervises by pressing her listening-in key, which act,

When the class-of-service sigsignal, that at the same time again actuates the classi of-service mechanism to guide her in making the charge or registration.

If the operator is unable for any reason to give the calling subscriber connection with the called line, she presses a holding key which maintains the connecting circuit in connection with the calling line, but withdraws the busy that it may call and be called. By listening in on a called line thus held, the operator is given a busy test if the line is in use, the class-of-service signal mechanism under these circumstances not being operated. If the line is free when the operator listens in on the held connect-ion, she may restore the holding key and proceed with the establishment'of the'connection in the usual way.

The features of the operation that have been set forth in outline in the foregoing, together with other features present in the system, will be fullyexplained in the detailed description that follows. I 1

' It will be assumed that the subscriber at station A takes his receiver from. its switchhook. The brushes 131, 132 and 133 of the distributor switch 130 areconstantly rotat-' ing, and thus are successively bringing the cut-in relay 11 and the test porary association with the various lines of the line group LG which the distributor switch 130 serves. If a line is in use either as a calling line or as a called line, its sleeve conductor 53 is connected through relatively low resistance with battery of the same potential as that to which the winding of the cut-in relay 11 is connected, as will hereinafter be explained. Consequently, when the distributor brush 133 engages the sleeve terminal of such line, the cut-in relay 1.1 remains inert. But when the-distributor brush 133 engages the sleeve terminal of a line that is not in use, an energizing path is closed for the cut-in relay 11 by way of the brush 133 and the sleeve resistance 91, or the message register 92 associated with that line. The test relay 12, therefore, is connected with the two line conductors 38 and 39 of each line that is not in use, and when it is thus connected with the conductors of the line extending to station A, at which the telephone receiver has been removed from its; switchhook, the test relay 12 attracts its armature and closes a circuitthat extends from battery through the winding of relay 9 to' ground by way of the front contact and armature of relay 12. Relay 9, in operating, closes a locking circuit for itselfby way of its left-hand front contact and armature and the left-hand back contact and armature of relay 10. The distributor brushes do not stop upon the terminals of'the calling line, but continue their rotation, the efi'ect of their engagetest from the line so' relay 12 into temmedium of a starting ment with the calling line terminals being in effect to record the call by energizing and locking up the relay 9.

The effect of recording the call upon the relay 9 is to cause the starting of one of the finder switches LF, LF, etc., whichv serve the lines of this and the associated line groups. This is accomplished through the circuit, two of the conductors '57 and 58 of which are extended to the relays 19 of the various line groups LG, LG, etc. Assuming that the starting circuit is not in use at the time the call is recorded on the relay 9 of the line group LG, the operation of this relay closes a circuit that extends from battery through the left-hand armature and back contact of relay 23, right-hand armature and back contact of relay 24, conductor 57, right-hand resting contact and switch spring of relay 19 of group LG, the windings of relay 19'and the associated trip magnet 17 in parallel, left-hand switch spring and resting contact of relay 19, right-hand winding of relay 18, and right-hand front contact and armature of relay 9 to ground. The closure of this circuit causes relay 18 to operate; and in operating relay 18 closes at its left-hand front contact and armature a shunt path by way of its left-hand low resistance winding to ground that sufiiciently increases the current flow in the circuit to bring about the operation of the relay 19 and its associated trip magnet 17, the relatively high resistance of the right-hand winding of the relay 18 pre- 'enting the relay 19 and its associated trip magnet from being operated at the initial closure of the circuit. Relay 19, in operating closes a circuit that extends from battery by way of the left-hand armature and back contact of relay 23, winding of the starting relay 24, conductor 58, the righthand armatures and resting contacts of other relays 19 in the series, right-hand-armature and switch spring of the relay 19 of group LG. the windings of relay 19 and associated trip magnet 17 in parallel, and the left-hand switch spring and armature of relay 19 to ground. The closure of this circuit operates relay 24 and the trip magnet of line group LG to start a line-finder switch and trip the brushes of that switch which correspond with the line group in which the calling line is located, as will hereinafter be described. This circuit is maintained and the trip magnet 17 starting relay 24, and group relay 19 held energized until the relay 2-3 is actuated at a later stage of the operation, as will be described.

When the recorded call has thus brought about the energization of the starting and brush-tripping circuit, the call recording apparatus including the relays 18, 9 and 10 is disconnected from the starting circuit and the record obliterated by the releasing and return of these relays to their normal condition. When the recording apparatus obtains access to the starting circuit, the operation of the relay 18 not only brings about the energization of the starting and tripping circuit by closing at its left-hand front contact and armature the low resistance path to ground; but it also closes a circuit that extendsfrom battery through the winding of relay 10, and the right-hand front contact and armature of relay 18 to ground. The closure of the circuit causes relay 10 to open, at its left-hand back contact and armature, the locking circuit of the relay 9.

Relay 9 in releasing opens at its right-hand front contact and armature, the'path to ground by way of the right-hand or high resistance winding of the relay 18. Relay 19, in operating, has opened at its left-hand switch spring and restlng contact, the main energizing circuit of the relay 18. Relay 18 therefore releases, and in doing so, opens It will be bserved that when the relay 10 operates, it closes a locking circuit for itself that extends by way of its right-hand front contact and armature, right-hand winding of relay 18, and right-hand front contact and armature of relay 9 to ground. This is for the purpose of insuring a continued interruption of the locking path-for relay 9, at the left-hand back contact and armature ofrelay 10, until the relay 9 is released. Otherwise it might happen that if the momentary operation of the relay 18, which operates relay 10, had occurred before the distributor brushes had passed beyond the calling line terminals and thus opened the initial energizing circuit of the recording relay 9, the recording relay would remain locked up and again energize the starting and tripping circuit as soon as that circuit again became available.

As the distributor switch brushes leave the terminals of the calling line, the test relay 12 is released. If in the meanwhile the call has been transferred to the starting circuit, in the manner described, the locking circuit of the recording relay 9 has been opened at the contacts of the relay 10, and the breaking of the initial energizing path of the relay 9 at contacts of the test relay 12 permits the relay 9 to release. The recording apparatus is therefore immediately in condition to respond to another calling line of the group, even though that line be the onewhose terminals immediately adjoin the terminals'of the line to which the apparatus has just responded. In this case the recording relay 9 is again locked up by and 10 of the recording apthe response of the test relay 12 as soon as the terminals of the second calling line are engaged," and remains locked up to bring about the energization of the starting circuit and the starting of another finder switch just as soon as the starting circuit is released and again made available by the operation of the relay 23, as will hereinafter be described. As long as the startin circuit is in use, the call in effect is store in the recording relay 9, andis made efi'ectl ve to start a finder switch as soon as the avallability of the starting circuit is restored.

As has been described, the approprlatlon of the starting circuit by an incoming call is accompanied by the operation of the relay 24, and the relay 24, in operating, disconnectsthe conductor 57 from ground. As it is over this path to ground that the initial energization of any of the relays 19 is effected, the calling lines of the other groups are deprived of control over their associated relay 19 and trip magnets until the starting relay 24 is returned to normal. If a line in another group, say group L'G', calls while the starting relay 24 is 'serving the calling line of group LG, the recording relay 9 of that other group is locked up and holds closed a path to ground from conductor 57 that includes the windings of the associated relay 19 and trip magnet 16 in parallel and the right-hand winding of the associated relay 18. When the starting relay 24 has performed its function in connection with the calling line of group LG and releases its armatures, the path by way of con ductor 57 is completed for the energization of the relays 18, 19 and 10 and the trip magnet 16 of group LG, in the manner that 1as been described in connection with the operation of these parts in group LG.

If calling lines in several groups are awaiting the starting relay 24, the recording relays 9 of these groups being locked up as a result of the momentary operation of the associated relays 12 as the distributor switch brushes pass over the terminals of the calling lines, the group, which is closest electrically to the starting relay 24:, will have its trip magnet operated and will take possession of the'starting circuit. The reason for this is that the conductor 58 that ineludes the windin of the starting relay 2A,

and over which the continued energization associated trip magnet is effected, passes serially through the righthand armature and resting contact of each of the relays 19, so that the relay 19 that is closest electrically to the relay 24 interrupts the path of the conductor 58 to the I more remote relays of'the series.

When the relay 19 of a group is energized by its seizure of the starting relay 24, it releases the associated relay 9, as has been described, and thus again rendersthe relay 9 vent the calling tends from battery by way of the operating, also cl switch contact 216 (2 to 3),

subject to the momentary operation of the test relay 12 as the brushes of the distributor switch 130 pass over the terminals of the lines of that group. In order to pre line from starting more than one line nder switch, the time required for the distributor .brushes to com plete a cycle of their rotation is so regulated that the calling line will have been seized by a finder switch, and thus deprived of its power to control the test relay12, before the distributor brushes have again moved into position to engage the terminals of that line.

The starting of a line finder switch when the common starting relay-24 is energized is t at ex- I effected by the closure of a circuit updrive magnet 32 of whichever of the line finder switches LF, LF', etc., is next in order to be started, conductor 59, line finder sequence switch contact 213 (2 to 2%), line finder sequence switch contact 217 (2), conductor 29, and left-hand armature and ,front contact of the starting relay 24: to ground. At the same time another circuit is completed from.

battery by way of the cord selector sequence switch contact 320 (1 to 4), winding of relay 30, selector sequence switch contact 309 (1 to 8), finder sequence switch contact 217 2), and thence to ground by way of conductor 29 and the left-hand armature and front contact of starting relay 24. Relay30, in operating, closes a circuit that extends from battery through the motor magnet and contact 203 (2) of the finder sequence switch, and right-hand front contact and armature of relay 30 to ground. The closure of this circuit moves the finder sequence switch 200 out of position 2. Relay 30, in oses a locking circuit for itself that extends from battery by'way of selector sequence switch contact 320 (1 to 4), winding of relay 30, selector sequence switch contact 309 (1 to 8), left-hand front contact and armature of relay 30, selector switch contact 317 (1), finder sequence conductor 25 and the right-hand back contact and armature of relay 23 to ground. v

When the finder sequence switch moves from position 2 to position 3, it closes a circuit from battery through updrive magnet 32, conductor 59, finder sequence switch contact 213 (2;- to-3) and the right-hand back contact and armature of test relay continued energization of the updrive magnet 32 under the control of the test relay 37.

the winding of I 37 to ground, that places the At the outset of the upward movement of the elevator 'rod 1 of the line-finder switch as a result of the ener ization of the updrive magnet 32, all of t e brush trip levers are moved ast the corresponding trip yokes 7. The on y trip magnet that 15 energized in this case is-the ma net 17 which corresponds with the group in which the callin line is located; and consequently the on y trip yoke in position to engage a trip lever on the elevator rod is the one which controls the brushes 40, 41, 42 and 43 that are adapted to engage the terminals of that particular group of lines. This set of rushes, therefore, is released and made operative, and the other sets are held clear of' their associated line terminals.

As soon as the set of brushes corresponding with the group in which the calling line is located is tripped, the group apparatus, by means of which the lines control the brush tripping and line finder starting operations, may be returned to its normal position. This is effected by the closure of a circuit which extends from battery by way of'the winding of relay 23, conductor 26,

, finder sequence switch contact 212 (2?; to 3),

conductor 68, and segment G of the linefinder commutator and its corresponding brush to ground. As a result the closure of this circuit which is timed to occur an instant after the brushes are tripped, and before they engage the line terminals in the upward movement of the elevator rod, relay 23 is energized to open, at its left-hand armature and back contact, the circuit by way of conductor 58 that up to this time has been holding the starting relay 24 and the trip magnet 17 and associated relay 19 energized. When, an instant later, the relay 23 is deenergized by the ground brush disengaging the commutator segment G, the group of starting circuits are again rendered responsive to a calling line.

When relay 23 operates it also interrupts at its right-hand armature and back contact the previously-traced circuit that has maintained relay 30 of the finder circuit energized. That relay, in releasing its armatures, closes a circuit for moving the finder sequence switch 200 of some other finder circuit from its normal or first position to position 2 where it is in readiness to respond to the next operation of the starting relay 24.

Assuming that the finder circuit F, which may. be assumed to be similar to the finder circuit F in its equipment, has its parts in their normal condition, this circuit may be traced from battery through the motor magnet 200 and contact 204 (1) of the finder circuit F, finder sequence switch contacts 204 (4 to 18) of other finder circuits similar to the circuits F which may be assumed to be busy, and therefore to have their sequence switches in some and F in their equipment,-

osition between position 4 and position 18 inclusive, finder sequence switch contact 221 (3) of finder circuit F, left-hand back contact and armature of relay 30, selector sequence switch contact 317 (1) finder sequence switch contact 216 (2 to 3), conductor 25, and right-hand back contact and armature of relay 23 to ground. Thus the passing of the G segment in the u ward movement of the started finder switc restores the group and starting circuits, releases relay 30 of the associated finder circuit, and moves sequence switch 200 of another finder circuit into position 2 in readiness to respond to the next actuation of the starting relay 24.

Provision is made for moving the finder sequence switch of one of the finder circuits into position 2, and thus rendering the associated circuit responsive to the starting relay, when all of the finder circuits are idle and have their finder sequence switches standing in position 1, or when all of them are busy and one is released to permit its finder sequence switch to return to position 1 while the sequence switches of all of the others are in some position between 4 and 18 inclusive. This is accomplished through the medium of the relay 20, which has its energizing circuit completed by way of conductor 28 and the series of finder sequence switch contacts 214 (4 to 1) to ground at the end of the series. When this condition of the series of finder sequnece switches exists, relay 20 is energized and closes a circuit that extends from the 204 cam series of all of the finder sequnece switches to ground by way of conductor 27 and the front contact and armature of relay 20. The closure of this path to ground energizes the motor magnet of one of the finder sequence switches 200 by way of the earn 204 (1) of the associated sequence switch to move that switch to position 2.

The condition that is now assumed to exist is one in which the line finder switch LF is moving up with its set of brushes corresponding with line group LG tripped, in

which the trip magnet 17 and relay 19 of that line group and the common starting relay 24 have been returned to their normal condition, and in which the finder sequence circuit is closed that extends from low potential battery by way of the relay 52, sequence switch contact 209 (2 to 3), conductor 50, brush42, line terminal 46, conductor 53, and windings of message register i 92 or xiesistance 91-to groundin the case of certain of the lines or by way of windingstracting its armatures closes a circuit that extends from battery through the left-hand windingof the relay 37 inner armature and front contact of relay 52, sequence SWItCh' contact 208 (2 to 3), conductor 49, brush 41, line terminal 45, conductor 39 to .onelimb ofthe telephone line, thence by way'of the path controlled in contacts of the substation switchhook to the other limb of the line,

conductor 38,,terminal' 44, brush 40, conductor 48, sequence switch contact 207 (2 to 3), outer front contact and armaturc of the relay 52, and right-hand winding of the relay 37 to ground. The circuit traced above is not completed until the finder switchbrushes engage the terminals of the calling line, as the calling line is the only line that has its telephone receiver oil the hook, and at the same time is not connected with either by some other line finder or by a connecting circuit calling plug. The completion of this .ingpositions, andthe line finder switches circuit energizes the relay 37 and causes that relay to interrupt at its right-hand back contact, the circuit by way of the finder sequence switch contact 213 (21k to 3) andf'conductor 59 which up to this time has been keeping the updrive magnet 32 energized and causing the upward movement of the switch brushes. Therefore 'theoperation of the relay 37 upon the finding of the calling line acts to efiect the instant deenerguzation of the updrive magnet 32 and thus to stop the brushes on the terminals of the calling line. a I Relay 37, in operating, also closes-a locking circuit for itself by way of its left-handfront contact and armature and finder se-- quence switch contact 219 (3) to grounds,

lt'also completes a circuit that-extends from battery through the motor magnet and con:-

tact 206 (3) of the finder sequence switch, and right-hand front contact and armature of relay 37 to ground. The closure of this circuit moves the finder sequence-switch out of pos1tion 3,

Provision 1s made for preventing the movement of the sequence switches 200 of more than one finder circuit into the'2 or waiting position in case an intermediate finder circuit returns .to its normal position before the started finder circuit has found the calling line and moved its sequence switch 200 out/of position 3. As has been 1 described, the passing of the G segment, by energizing and then releasing relay 23, applies ground by way of conductor 25, finder sequence switch contact216 (2 to 3), selector sequence switch contact 317 (1), left-hand armature and back contact of relay 30, and findcr sequence switch contact 221 (3), for moving out of its normal or 1 position the finder sequence switch of the next finder circuit in the series-which is standing in that position. Let it be assumed that the finder while itssequence switch 200 is still resting in position 3,the finder circuit F is freed and its sequence switch 200 returned to nor mal. If, under these circumstances, the

ground from the back contact of relay 23 should still applied by wayof the back contact of relay 30 and finder sequence switch contact 221 (3) of the finder circuit that is hunting for the calling line, the finder sequence switch of finder circuit F would also bemoved out of position 1 as soon as it was returned thereto, so that the finder sequence switches of circuits F and 1 F' would both be resting in their 2 or waitof both circuits would be started in response to the next call. To prevent this a common conductor 75 is provided, this conductor havlng a branch which connects with the finder sequence switch contacts 218 ("1%) and 217- (3) of each of the finder circuits of the group. As a result, when the sequence switch 200 of finder circuit F is moved out of position 1 in response to the passing of the G segment of finder circuit F as the line'finder switch starts up, it closes a circuit that exlot tends from battery through selector, sequence switch contact 320 (1 to 4) of finder circuit F, winding of relay 30, selector sequence switch contact 309 (1 to 8), finder sequence switch contact 217 (3), conductor 75, and

finder sequence switch contact 218 (1%) of finder circuit F to ground. Relay 30 oper ates and locks up by way of the path which extends through its left-hand frontcontact and armature, selector sequence switch contact 317 1) finder sequence switch contact 216 (2 to 3),'conductor 25, and the right-hand back contact and armature of relay 23 to ground.- Relay 30 therefore breaks, at its left-hand armature and back contact, the path over which ground from the back contact of relay 23 would otherwise be applied by way of finder sequence switch contact 221 (3) to move the sequence switch 200 of finder circontact 213-(2 to 3) by the movement of the finder switch out'of position 3 upon'the finding of the calling line. This same movement of the finder sequence switch also'interrupts, at sequence switch contact 221 (3),

the path for moving the finder sequence switch of any other finder circuit out of position 1. Therefore the grounding of conductor 7 5 when any finder sequence switch is moved out of position 1, prevents the movement out of position 1 of any intermediate finder sequence switch whose finder circuit may be released while the finder sequence switchof the started finder circuit is resting in position 3.

In moving to position 4 upon the finding of the calling line, the finder sequence switch closes a circuit that extends from battery, by way of resistance coil 54: and sequence switch contact 210 (4 to 4%), to the sleeve conductor 50 of the finder circuit, and thence by way of the finder switch to the sleeve condoctor 53 of the calling subscribers line. This creates an electrical condition upon the line that prevents it thereafter from afiecting the distributor test magnets 11 and 12, and that prevents it from being connected with by an other line. In moving to position 4 the nder sequence switch also closes a circuit that extends from battery through the. motor magnet and contact 302 (1) of the selector sequence switch, contact 220 (4) of the finder sequence switch, and right-hand back contact and armature of relay 37 to ground. The closure of this circuit moves the selector sequence switch out of position 1 and into position 2.

The next stages of the operation of the s stem have to do with the selection by the nder circuit of an available operators position. The selection of the operators position is effected throu h the medium of an operators selecting circuit that is common to all of the group of finder circuits of which the finder circuit F is one. Before the finder circuit F is given access to the 'operators selecting circuit, it is necessary that the circuit shall have been set free by any other one of the group of finder circuits which may have been employing it.

The circuit that controls the movement of the selector sequence switch 300 out of position 2 extends om battery, through the m0- tor magnet and contacts 303 (2) and 313 (2) of the selector sequence switch, and t ence by way of conductor 7 6 and the lefthand back contacts and armatures of the relays 61 and 63 of the operators selecting circuit in series to ground. As will hereinafter m described, one or the other of the relays 61 and 63 is energized irom the instant a finder circuit of the cup obtains possession of the operators se ecting circuit until the selecting circuit has performed its tor sequence switch out of position 2, is continned through the selector sequence switch contacts 303 (6 to 1) of all of the finder circuits in series. As a result, any of the selector sequence switches in moving into position 2 breaks, at its sequence switch contact 313 (Sto 1), the pathof the conductor 76 to all of the selector sequence switch contacts beyond it in the series. Conse uently, if there should happen to be two fin er circuits awaiting access to the operators selecting circuit, only the one closer electrically to the controlling relays 61 and 63 would be moved out of osition 2 when the selecting circuit was re eased and the armatures of relays 61 and 63 retracted, the more remote finder circuits in the electrical series being obliged to wait until its energizing circuit is closed by themovement to position 6 of the selector sequence switch ahead of it in the Series. V

When the finder circuit F obtains access to the operators selecting circuit by the movement of the selector sequence switch 300 into position 3, a circuit is closed that extends from battery through the winding of relay 31, the left-hand switch-spring and resting contact of that relay, conductor 73, and selector sequence switchcontact 311 (25} to 3) to ground. The relay 61 in operating closes a holding circuit for itself by way of its left-hand switch-spring and armature and the left-hand back contact and armature of relay 63 to ground. The relay 6]. at the same time closes, at its right-hand switchs gging and armature, a circuit that brings a ut the selection of one of the operators positions which happens at the time to be available, and the energization of the selector-switch trip magnet corresponding to that position.

The availability or unavailability of each of the various operrlors positions is determined by the conoition of the relay 77 as-' sociated with that operators position in the operators selecting circuit; and that in turn is determined by the condition of operators position apparatus that marks whether or not the operator is at her position and in readiness to receive a call. The particular conditions upon which the energization or deenergization of the relay 77 de nds will be described hereinafter. For t epresent it will be sufiicient to say that if'the operator is not at'her position, a circuit is completed that extends from battery through the left-hand winding of the associated relay 77 of the operators selecting circuit, the right-hand back contact and armature of the associated relay 93, conductor 82, swltch spring 197 and resting contact of the o eraltors telephone jack 195 .to ground. f the operator is at her position, and the selecting apparatus hasjust operated to assign a-call to that position, the path to ground for energizing-the associated relay 77 is completed by wa of conductor 82, switch spring 197 and a ternate contact of the operators telephone jack 195-.and the r1ghts hand front contact and armature of relay 148. If the operator is at. her position, and the call assigned to that positlon'has reached one of the connecting cord circuits, then the path to ground for'the energization of the associated relay 77 is completed by way of switch spring 197 and alternate contact of .the operators telephone jack 195, conductor 241 and contact 411 kev sequence switch.

- When the relay 61 of the operators selecting circuitis operated. in the manner hereinbefore described, the attraction "of its right-hand armature extends the conductor (2 to 6) of the listening 141 to ground by wayof the resting contact and armature of relay 67. The conductor 141 includes contacts of the entire seriesof relays 77 associated with the various operators" positions in the operators selectlng circuit. The arrangement is such that each relay 77 when unergized extends the conductor 141 to the winding of the associated relay 93, and when energized extends the circuit of the conductor to the next relay 77 in the series. Assuming now that the first operators position in the series is avallablc when the relay 61 is operated, a c1rcu1t 18 completed that extends from battery by way of the left-hand armature and back contact of relay 159 (see Fig. 5), the upper armature and back contact of relay 147, conductor 83. left-hand back contact and swltch spring of relay 93, winding of that relay, back contact and armature of associated relay 7 7,

, conductor 141, right-hand armature and switch spring of relay 61 and back contact. and armature of relay 67 to ground. Relay 93 operates as a result of the closure of this circuit, and in attracting its left-hand armature substitutes for the energizing path by 'way of the upper'armature and back contact of relay 147 and conductor 83, a branch energizing path that extends by way of the winding of relay 147 and'conductor 84 to the left-hand armature and switch spring-of relay 93, and thence through the winding of relay 93 and to ground as already traced.

83 to the relays 93 associated with this particular operators position upon the different sw1tc'h frames, frame 1, frame 2, etc.,

that have access, to this position. 3 As the initial energization of the. relays 93 associated with a particular opcrators position on w the venous frames must be etfected through the medium of the common conductor 83, the opening of this conductor at the upper back contact and armature of relay 147 instantly'renders the position unselectable at any other cord selector frame. Also, the series relation that exists between the relays 93 of any operators position with respect tothe permanent energizing path 84 of these relays, assures that only one of the relays 93 will be permanently energized in case it is assumed that two calls originating in difi'erent frames attempt to gain access to the same operators position at the same instant. In such a case, the operation of the relay 93 of the frame closer electrically to the relay 147 opens the path of the energizing conductor 84 to the relay 93 of the more remote frame.

When the relay 147 is energized as a result I of the selection of'the associated operators position, in the manner described above, it closes a circuit that extends from battery through the winding of relay 156, upper back contact and armature of relay 157, and lower front contact and armature of relay 147 to ground. The relay 156, in operating, closes at its lower front contact and armature, a circuit that causes the lighting of the operators position lamp 167, and the lighting of this lamp notifies the operator that her position has been selected and that a call is being extended to one of her connecting cord circuits, the particular circuit that has been selected being indicated a few moments later by the lighting of the lamp 341 associated with that particular circuit. as will hereinafter be described. Relay 147, in operating, upon the selection of the operators position, also closes a circuit that extends from the 'battery through the left-hand armature and back contact of relay 159, winding. of relay 148 and lower front contact and armature of relay 147 to ground. When the relay 148 operates, it closes a circuit that extends from battery through the winding of relay 64 (see 'Fig. 3), the winding of trip magnet 22 associated with the selected onerators position on the selector switch, right-hand frontcontact and armature of re lay 93, conductor 82, switch spring 197 and alternate contact of-the operators telephone jack 195, and right-hand fro'nt contact and armature of relay. 148 to ground. The closure of this circuit energizes the trip magnet 22; and also operates relay 64 to close a the connectin 1 I circuit that extends from battery through the motor magnet and contact 303 (3) of thetord selector se uence switch (see Fig.

2), conductor 72, an the front contact and armature of relay 64 to ground. The closure of this circuit moves the sequence switch 300 out of position 3.

When the selector sequence'switch reaches position 4, a circuit is completed that extends from battery through the motor magnet and contact 304 (4) of the sele.tor sequence switch and the right-hand back contact and armature of relay.30 to ground, and as a result of the closure of this circuit the sequence switch is moved to position 5. When the sequence switch reaches position 5, a circuit is c osed that extends from battery through the winding of the updrive magnet 34, conductor 89, selector se uence sw1tch contact 316 (5 to 6) and rig t-hand back contact and armature of relay 30 to ground. The updrive magnet 34 in attracting its armature starts the upward movement of the switch brushes. At the outset of the upward movement of the brushes the tripping levers of all of the sets of brushes move into position to engage the tripping yokes 7 at the various levels corresponding with the variousopcrators positions. In'the present instance, it is assumed that the trip1 magnet 22 is energized, and as a result t e tripping yoke corresponding with that magnet is in position to engage the tripping lever of the corresponding set of brushes, and that set of brushes is tri pad and made operative.

Immediatey after the brush-tripping position is passed in the upward movement of the switch, and before the brushes engage cord terminals of the corresponding ban the commutator se ent G is engaged by theassociated groun ed commutator brush. This closes a circuit that extends from battery through contact 306 (5) of the selector sequence switch, the low resistance left-hand winding and high resistance right-hand winding of relay 56 in series, contacts 315 (5) of the selector sequence switch, contact 312 (5) of that switch, conductor 80, and to ground by way of the G segment and corresponding brush of the cord selector commutator. elay 56, in operating, closes a locking circuit for itself that'extends to ground by way of contact 315 (5) of the cord selector sequence switch, right-hand front contact and armature of relay 56, and selector sequence switch contact 318 (5). Relay 56, in operating, also closes a circuit that extends from battery byway of the motor magnet and contact 304 (5) of the selector sequence switch, and left-hand switch spring and armature of relay 56 to ground. This causes the movement of the selector sequence switch out of position 5 and into position 6. 1

When the cord selector brushes have been ing of rela tri ped, the operators selection is completed, an the operators selecting circuit may be released to become available for performing its function in connection with the extension of another call. Therefore, as the grounded brush engages the G segment of the cord selector commutator a circuit is completed that extends from battery through the wind- 63 of the operators selecting circuit, con uctor 74, contact 312 (5) ofthe selector sequence switch, conductor 80, and G segment and corresponding brush ofthe cord selector commutator to ground. Belay 63, in operating closes 'at its right-hand front contact and armature a locking circuit for itself that extends by way of the righthand armature and switch s ring of relay 61, and the back contact and armature of relay 67 to ound. Rela 63 also opens, at its left-han armature an back contact, the circuit which, from the moment relay 61 was first operated, has been maintaining that relay energized. Consequently, relay 61 re,- leases its armatures and in doing so, opens the locking circuit for relay 63, which relay in turn is deenergized and released. The restoration of both the relays 61 and 63 again completes the connection of conductor 76 to ground, so that this path is again available for moving out of position 2, the selector sequence switch of any other finder circuit that may be awaiting access to the operators selecting circuit.

Relay 61, in releasing, also opens at its right-hand armature and switch spring, the path to ground over which the relay 93 of the operators selecting circuit and relay 147 of the operators position circuit have been held energized. Relay 93, in releasing, opens the energizing circuit of the trip ma et 22 and closes a circuit that extends rom batter through left-hand winding of'the relay 7, right-hand back contact and arm! ture of relay 93, conductor 82, switch spring 197 and alternate contact of the operators telephone jack 195, and to ground by the divided path one branch of which extends by way of the right-hand front contact and armature of relay 148 and the other of which extends by way of contact 411 (2 to 6) of the listening key sequence switch 400 when that sequence switch is moved out of position 1. as will subsequently be described.

Relay 77 therefore becomes energized, and remains energized as long as the operator is 

